Letter U Firearms Glossary

Arsenal Exchange - Firearms Classifieds - Industry Directory

Underbolts

A sliding bar, running longitudinally through the watertable of a break-open side-by-side gun's action, with openings through which the lumps of the barrels pass when the gun is closed. Under spring tension, this bar moves forward when the opening control is released and its two locking surfaces engage complementary slots (bites) in the rear of the two barrel lumps. Originally operated by a hinged tab in front of the trigger guard. Now invariably operated by a cam from Scott's [toplever] spindle. Most modern side-by-side guns lock closed in this manner.

Underhammer

A type of lock in which the hammer pivots in a vertical arc, striking the nipple on the underside of the barrel. Since the nipple's flash channel goes straight into the powder at the breech end of the barrel, ignition time is very fast. For this reason, and because it gets the hammer out of the way, underhammer locks are commonly used on muzzleloading benchrest rifles which are used for target shooting, and where accuracy is the goal.

Underlug

The locking lugs on a break-action firearm that extend from the bottom of the barrels under the chamber(s) and connect into the receiver bottom.

Underwater Firearm

A firearm specially designed for use underwater.

Upset Forging

A process that increases the diameter of a workpiece by compressing its length.


14 Other Firearms Definitions You Need To Know


Cant

To tilt a gun to one side or the other, complicating sighting considerably. Can cause material loss of accuracy, particularly with a rifle at longer ranges. Some better long range target rifles are equipped with Spirit Level sights to help control canting.

Erosion

The wearing away of a barrel's metal surface by a bullet or shot charge or by the heat of powder gases.

Trace

Visible disturbance in the air by a bullet. Typically this takes the form of image distortion that persists for a fraction of a second in the shape of an inverted V similar to that of a boat wake.

Firing Pin

A needle like metal part of a modern firearm that gives a vigorous strike to the primer initiating the firing of the cartridge.

Magnum

From the Latin for "more." A term indicating a relatively heavily loaded metallic cartridge or shotshell and a gun safely constructed to fire it. It generally indicates a round which cannot be interchanged with other loadings of the same caliber (for example, a .22 Magnum shell does not fit within a firearm designed to fire .22 Long Rifle ammunition).

Ejector

A spring-activated mechanism for the ejection of ammunition or and empty shell casing. On doubles, each barrel has a separate ejector.

Tangent Sight

A style of rear sight, typically used on rifles for either slow-moving bullets or for long ranges, whereby a ladder may be raised from flush with the barrel to a vertical position, and which incorporates a sliding crossbar which may be moved vertically in order to achieve significant elevation.

AE

Abbreviation for Arsenal Exchange or ArsenalExchange.com. Example in a sentence is "Have you seen the latest postings on AE?
AE is also the abreviation for Action Express. .50 Action Express (.50 AE) is a large caliber handgun cartridge. It was developed in 1988 by Evan Whildin of Action Arms.

Break Action

A firearm whose barrels are hinged, and rotate perpendicular to the bore axis to expose the breech and allow loading and unloading of ammunition.

Shell

An empty ammunition case.

Projectile

A bullet or shot in flight after discharge from a firearm.

Half grip

Round knob, semi pistol grip.

Standing Breech

The face of the action of a break-open firearm which houses the firing pins and receives the direct recoil of the fired round.

Gloaming Sight

A second, folding or pop-up front sight bead of larger than usual size, perhaps not as accurate as a normal fine bead, but easier to see in the gloaming (twilight) or dawn.

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